Apparatus and method for rapid photo-thermal surface treatment

ABSTRACT

An apparatus for surface treating a semiconductor wafer includes a surface treatment chamber and a source of radiation. The semiconductor wafer disposed inside the chamber is illuminated with radiation sufficient to create a plurality of electron-hole pairs near the surface of the wafer and to desorb ions and molecules adsorbed on the surface of the wafer.

FIELD OF THE INVENTION

[0001] The invention relates to an apparatus and method for processing asemiconductor, and more specifically, relates to an apparatus and methodfor surface treating a semiconductor wafer in preparation for an in-linemonitoring procedure.

BACKGROUND OF THE INVENTION

[0002] Operation of an integrated circuit (IC) depends on the electricalproperties of materials of which the circuit is formed. Therefore, bymonitoring selected electrical properties of these materials in thecourse of an IC fabrication, an effective control over the manufacturingprocess can be accomplished. Since modern ICs are typically formed inthe shallow region below the surface of a semiconductor wafer, criticalelectrical properties are directly or indirectly related to thecondition of the surface region of the semiconductor wafer. Surfaceproperties of a semiconductor wafer can be monitored during ICfabrication through in-line monitoring procedures such as described inU.S. Pat. No. 4,544,887 and U.S. Pat. No. 5,661,408.

[0003] The in-line monitoring procedure permits surface properties of asemiconductor wafer to be measured without contacting the wafer surface,so that the surface properties are not affected by the measurementitself However, unlike conventional methods of electricalcharacterization in which contaminant ions and molecules from theambient environment do not significantly affect the measurements due toformation of a permanent contact on the surface of the wafer,non-contact measurements may not provide accurate information about thewafer. This is because contaminant ions and molecules from the ambientenvironment may adsorb on the surface of the wafer during transportationand storage, changing surface properties of the wafer. Consequently, itmay-be difficult to obtain accurate information about the surfaceproperties of the semiconductors with the in-line monitoring proceduresunless the semiconductors are surface treated prior to being measured.

[0004] According to one known method, a p-type silicon wafer is surfacetreated by being immersed in dilute hydrofluoric acid, rinsed withdeionized water and dried in order to restore an inversion condition. Awidth of surface depletion layer measured under an inversion conditionprovides net doping concentration in the sub-surface region. Existingsurface preparation steps, however, are typically not integrated withsubsequent measurement steps. In addition, existing processing andmonitoring methods are not capable of establishing the surface conditionof a wafer by means of a simple treatment in ambient environment atatmospheric pressure as needed to carry out a specific electricalmeasurement.

[0005] Therefore, there is a need for an apparatus and method whichdetermine selected electrical parameters of semiconductor wafersrepresenting the outcome of individual processing steps, independent ofthe ambient atmosphere in which the wafers are stored or transported.

SUMMARY OF THE INVENTION

[0006] It is an object of the invention to provide a surface treatmentapparatus and method, which reduce the affect of ambient environment, inwhich a wafer is transported or stored between processing steps, on thewafer surface condition. It is another object of the invention toprovide a surface treatment apparatus and method which can be integratedwith an in-line monitoring apparatus and method.

[0007] In one aspect, the invention features a method for in-line,real-time monitoring of a semiconductor wafer. According to the method,a plurality of electron-hole pairs are created near a surface of thewafer and the wafer is heated to substantially desorb any of a pluralityof contaminant ions and molecules adsorbed on the surface of the wafer.In one embodiment, the plurality of electron-hole pairs are created byilluminating the wafer with a radiation of photon energy sufficient tocreate the plurality of electron-hole pairs. In another embodiment, thewafer is heated by illuminating the wafer with a near infraredradiation. In still another embodiment, the wafer is a p-type wafer andheating and illuminating the p-type wafer restores an inversion layer onthe surface of the p-type wafer.

[0008] In another aspect, the invention features an apparatus forsurface treating a semiconductor wafer. The apparatus includes a surfacetreatment chamber and a source of radiation, which illuminates asemiconductor wafer disposed inside the chamber with radiationsufficient to create a plurality of electron-hole pairs near a surfaceof the wafer and to desorb any of a plurality of ions and moleculesadsorbed on the surface of the wafer. In one embodiment, the surfacetreatment chamber is integrated with an in-line, real-time testingapparatus such that a surface photovoltage of the wafer can be measuredafter the wafer has been surface treated. In another embodiment, theapparatus further comprises a power control circuitry for controlling anintensity of radiation from the radiation source.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The invention is pointed out with particularity in the appendedclaims. The above and further advantages of this invention may be betterunderstood by referring to the following description taken inconjunction with the accompanying drawings, in which:

[0010]FIG. 1 is a graph illustrating time dependence of a surface chargemeasured on a p-type CZ silicon wafer sequentially exposed to clean roomair, stored in a box and exposed again to clean room air.

[0011]FIG. 2 is a graph illustrating time dependence of a surface chargemeasured on an n-type CZ silicon wafer sequentially stored in a box,exposed to clean room air, and again stored in a box.

[0012]FIGS. 3a-e illustrate adsorption of contaminant ions and moleculesfrom the ambient environment on a surface of a semiconductor wafer anddesorption of the contaminant ions and molecules from the wafer surfacethrough a subsequent photo-thermal treatment of the invention.

[0013]FIG. 4 is a graph comparing the surface charges of two p-typesilicon wafers grown in the same batch, one as-grown and the other RCAcleaned (SC1+SC2), immediately after fabrication, after storage for 12weeks, and after photo-thermal treatment.

[0014]FIG. 5 is a schematic diagram of an embodiment of an apparatus ofthe invention for photo-thermal surface treatment of a semiconductorwafer.

[0015]FIG. 6 is a graph illustrating dependence of electricalcharacteristics of two p/p+ silicon epitaxial wafers on peak temperatureduring photo-thermal treatment at constant processing time of 30seconds.

[0016]FIG. 7 is a graph comparing deviations of the apparent dopingconcentration measured in as-grown p-type silicon wafers before andafter photo-thermal treatment at peak temperature of 250° C.

[0017]FIG. 8 is a graph comparing deviations of the apparent dopingconcentration measured in RCA cleaned p-type silicon wafers before andafter photo-thermal treatment at peak temperature of 250° C.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] The surface condition of a semiconductor wafer depends on surfacepreparation as well as the wafer's surrounding ambient environment,which may be in gaseous, vapor, or liquid phase. In general, surfaces ofsemiconductor wafers tend to reach equilibrium with the surroundingambient environment. Therefore, ions and molecules present in theambient environment may adsorb to surfaces of the wafers exposed to theambient environment, and changes in the ambient environment compositionwill also cause changes in the layer adsorbed to the surface. The effectof the gaseous ambient environment on the surfaces of wafers have beenrecognized and utilized by those skilled in the art, for example, as ameans of varying the surface potential barrier height in germanium.

[0019] Referring to FIGS. 1 and 2, the surface charge in silicon wafersvaries as the ambient environment changes. FIG. 1 shows surface chargevariation in a p-type wafer as a function of time and storageconditions. In FIG. 1, the p-type wafer is first exposed to a clean roomair for approximately 70 minutes, stored in a covered box forapproximately 800 minutes, and again exposed to the clean room air forapproximately 225 minutes. The surface charge in the p-type wafer ismeasured using the surface photo-voltage method as described in U.S.Pat. No. 4,544,887 issued on Oct. 1, 1985 and U.S. Pat. No. 5,661,408issued on Aug. 26, 1997, both assigned to the assignee of the presentinvention. FIG. 2 similarly shows surface charge variation in an n-typewafer. In FIG. 2, the n-type wafer is sequentially stored in a box forapproximately 740 minutes, exposed to clean air for approximately 300minutes, and again stored in a box for approximately 300 minutes. Thesurface charge of the n-type wafer is also derived from surface photovoltage measurements. The surface charge measurements shown in FIGS. 1and 2 demonstrate the sensitivity of the silicon surface charge to theclean-room and the storage container ambient environment conditions.While the magnitude of the surface charge variations for p-type andn-type wafers as shown in FIGS. 1 and 2 differs, the polarity of thechanges is the same, independent of the conductivity type of the wafer.Exposure to clean-room air results in more negative surface charges andstorage in the container results in more positive charges forming at thewafer surface. The difference in the polarity of the surface chargechanges can be attributed to the difference in the composition of theclean-room and the box ambient environments. It has been observed by theinventor that the rate of change in the surface charge depends on thesurface preparation, and composition of water-based cleaning solutionsused in cleaning the wafers.

[0020] FIGS. 3(a-e) show an evolution of the contamination of a siliconwafer surface due to its interaction with a surrounding environment. Acrystalline silicon wafer (FIG. 3a) has a positive charge 10 associatedwith the lack of bonds to atoms at the wafer surface as symbolicallyillustrated in FIG. 3a. However, such an abruptly terminated surface isinherently unstable, and other species from the surrounding ambientenvironment will adsorb on the surface of the wafer 12. The atoms in afew top monolayers of the silicon crystal may also rearrange theirconfiguration resulting in a more gradual transition from the surface tothe bulk crystalline structure. In this case, the positive chargeassociated with the crystal termination will be distributed across a fewtop monolayers.

[0021] The stability of such bare silicon surface will depend on itsprior history. However, given enough time, the exposure of the siliconsurface to the surrounding environment will result in the formation of athin native oxide layer 14 as illustrated in (FIG. 3b). Similarly, athin chemical oxide film could be formed on the silicon wafer surface 12when the wafer is subjected to a cleaning procedure, such as an RCAclean. The positive charge at a wafer surface associated with crystaltermination will spread into the oxide in both cases. However, asillustrated in FIG. 3b, negative ions 16 from the ambient environmentcan interact with the wafer surface 12 during or before oxide formation.These interactions with negative ions 16 from the ambient environmentmay result in adsorption of these species to the surface of the wafer 12with the resulting contamination of the native or chemical oxide layer14. Negative ions 16 from the ambient environment reduce positive oxidecharge. Examples of such contaminants, in the case of the RCA clean, arealuminum and iron.

[0022] Neutral polar molecules 18 from the liquid ambient environment(e.g., water or alcohol) may adsorb on the oxide layer 14 of the wafersurface 12, resulting in formation of a double-layer 20 as shown in FIG.3c. The double-layer 20 can also result from adsorption of polarmolecules 18 from the air (FIG. 3c). The double layer may also containsome negative ions and species 22, 24, again reducing positive charge atthe surface of the wafer. It can be expected that the transition fromthe virgin surface (shown in FIG. 3a) to a double-layer 20 coatedsurface (FIG. 3c) will take longer than transition from the oxidizedsurface 14 (FIG. 3b) to the double-layer 20 coated surface FIG. 3c. Thisprinciple is illustrated in FIG. 4, which compares evolution of twop-type silicon epitaxial wafers grown in the same batch, during storageand after photo-thermal surface treatment. One wafer, labeled as“as-grown”, was not subject to any cleaning, while the other wafer,labeled “SC1+SC2”, was subject to an oxidizing clean. The graph in FIG.4 shows that the surface charge of the two wafers immediately afterremoval from the shipping containers is already substantially different,and both deviate from the target surface charge represented by a dashline. The RCA-treated wafer shows less positive charge than the as-grownwafer. The difference between the wafers increase even more after thewafers are stored in a container for further 12-weeks, illustrating thatcharge variation in RCA-treated wafer occurs faster than in anon-treated wafer. The graph in FIG. 4 also shows that photo-thermalsurface treatment of the present invention restore the positive surfacecharge on both wafers approximately to the target value.

[0023] Referring to FIG. 3d, the present invention features aphoto-thermal surface treatment method and an apparatus for removing orneutralizing surface charges associated with the double layer 20.According to the invention, a plurality of electron-hole pairs 30 arecreated near the surface of the wafer 12 by illuminating the wafer.Creation of the electron-hole pairs 30 weakens the strength with whichnon-volatile ions and molecules of the double layer 20 are adsorbed tothe oxide layer 14. The wafer is also heated to substantially desorbvolatile contaminant ions and molecules adsorbed on the surface of thewafer 12. As the volatile contaminant ions and molecules, includingpolar molecules 18 forming a double layer 20 desorb, they carry away thenon-volatile contaminant ions and molecules 22, 24 as well. Therefore,after photo-thermal surface treatment, the surface charge properties ofthe wafer is returned to its state prior to formation of the doublelayer 20 as shown in FIG. 3e.

[0024] In the case of p-type silicon wafers, the positive surface chargeinduces an inversion condition at the surface by repelling positivelycharged free holes from the surface region. Therefore, the photo-thermalsurface treatment restoring the positive surface charge will alsorestore inversion conditions at the surface. This allows theestablishment of reference conditions at the semiconductor surface forthe measurement of the basic electrical parameters such as dopingconcentration and surface recombination lifetime. The photo-thermalsurface treatment of p-type silicon wafers may also allow activating ofdopants such as boron, which were deactivated due to interaction withhydrogen or metal atoms.

[0025] The invention makes use of optical radiation 32 (FIG. 3d) underdefined conditions to remove species adsorbed on the surface 12 of asemiconductor wafer 11 due to interaction with an ambient environment.In this method, a uniform beam of light 32 is directed at the surface 12of the semiconductor wafer 11, illuminating the wafer 11. Theilluminating light 32 comprises a combination of short and longwavelength light. The short wavelength light has wavelengths greaterthan that corresponding to the energy gap of the semiconductor material.The long wavelength light has wavelength in the near infrared range. Thelight with the wavelength greater than the band gap generates a highdensity of free electrons and holes 30 (FIG. 3d) near the semiconductorsurface 12 and heats the wafer 11. The light in the near infrared rangefurther increases the temperature of the semiconductor surface 12 tothat required to desorb or evaporate volatile molecular species adsorbedon the surface 12. As the volatile species desorb, they carry awayother, non-volatile ions and molecules adsorbed to the surface 12 of thewafer 11.

[0026] The effect of photo-thermal surface treatment of a wafer can bemonitored by measuring the AC surface photovoltage of the wafer underconditions disclosed in U.S. Pat. No. 4,544,887 and U.S. Pat. No.5,661,408. The conditions of the wafer treatment, temperature andillumination time are determined based on these measurements.

[0027] Referring to FIG. 5, an apparatus for photo-thermal surfacetreatment includes two major parts: a wafer-processing module 40 and apower control circuitry 42. The wafer-processing module 40 includes alight source unit 44 integrated with the wafer processing chamber 46.The light source unit 44 is capable of generating light havingwavelengths sufficient to generate free electron-hole pairs near thesurface of the wafer and near infrared light. In the embodiment of FIG.5, the light is provided by tungsten halogen quartz lamps 48. The lamps48 provide the light in the spectral range from about 0.2 μm to about 4μm. The lamps 48 are mounted to a water-cooled top light reflector 52with ceramic lamp supports 50. In an alternative embodiment, a hot plateor a furnace is used to heat the wafer, while the light source providesthe short wavelengths light. The wafer is heated to a temperature in therange from about 200° C. to about 300° C. The top light reflector 52includes a series of parabolic reflectors 53 which provide uniformillumination over the entire wafer located in the processing chamber 46.

[0028] In one embodiment, the light source 44 may comprise 10 tubularquartz halogen lamps of 1000 Watts each. In this embodiment, thedistance between the lamps may be approximately 20 mm. To compensate forthe decrease in light intensity at the periphery of the illuminatedarea, the water-cooled side reflectors 54 are added on all four sides ofthe process chamber 46. Alternatively, these four side reflectors 54 maybe replaced by a cylindrical reflector with a diameter slightlyexceeding the diameter of the wafer 56. The diameter of the cylindricalreflector, for example, may exceed the diameter of the wafer 56 by about20 mm. The side reflectors 54 extend below the plane of wafer 56, whenthe wafer 56 is disposed on a wafer support 58 in the process chamber46.

[0029] The apparatus further includes a water-cooled bottom lightreflector 60 under the wafer 56 to improve the uniformity of the light.In one embodiment, the wafer 56 is supported by three thermallyinsulating pins 58 manufactured from Vespel® provided by DuPont Company(Wilmington, Del.) arranged in a triangular configuration. The top, sideand bottom light reflectors 52, 54, 60 form a “black-body” box,uniformly illuminating the chamber 46 due to multiple scattering. Lightuniformity in the embodiment of FIG. 5 has been measured. At thedistance of about 100 mm below the lamps 48, the light uniformity was±5% across an area 200 mm in diameter. The distance of 100 mm below thelamps 48 corresponds to wafer location.

[0030] In the embodiment of FIG. 5, the power control circuitry 42 is incommunication with the wafer-processing module 40 in a closed-loop. Theintensity of light illuminating the wafer 56 is controlled by measuringradiation from the wafer 56 with an infrared sensor 62 located beneaththe wafer 56. In one detailed embodiment, the sensor 62 is located about25 mm beneath the wafer 56. The radiation information is used to controlthe intensity of light illuminating the wafer 56.

[0031] The infrared sensor 62 is sensitive only to the radiation ofwavelengths between 6.5 μm and 14 μm, and therefore, measures radiationemitted by the wafer 56 and not the light source 44. The signal from theinfrared sensor 62 is fed into a lamp power controller 74 which controlspower supplied to the lamps 48, and hence controls intensity of thelight illuminating the wafer 56. The controller 74 is programmedmanually or via a connection to a computer 72 for the wafer 56 to reacha predetermined temperature and then to maintain this temperature for apredetermined time.

[0032] To provide accurate measurement of the wafer temperature, thewafer-processing module 40 further includes a set of optical filters 64,66 made of quartz. The set of optical filters 64, 66 filters infraredradiation from the lamps 48 exceeding wavelength of approximately 4 μm,such that the temperature detected by the sensor 62 results from thewafer radiation only. The first quartz filter 64 absorbs light havingwavelength exceeding about 4 μm. The absorption of light causes thisfilter 64 to warm up and to emit infrared radiation of wavelengthslonger than 4 μm. This radiation is subsequently absorbed by the secondquartz filter 66. The quartz filters 64, 66 are cooled down by airpassing through a passageway 68 between the filters 64, 66. In oneembodiment, an electrical fan forces air through the inlet 70 of thepassageway 68.

[0033] The light source 44, in combination with the filters 64, 66produce light having wavelengths of less than about 4 μm. This lightilluminating the wafer 56 is capable of generating free electron-holepairs near the surface of the wafer and heating the wafer to atemperature sufficient to desorb contaminant ions and molecules. Theradiation emitted by the heated wafer 56 is measured using the infraredsensor 62.

[0034] After completion of the illumination cycle, the power applied tothe lamps 48 is turned off and the wafer 56 is left to cool down to aroom temperature. Alternatively, the three wafer support pins 58 can beretracted causing the wafer 56 to get in a close proximity or touch thewater cooled bottom reflector 60 to speed up the wafer cooling process.During the cooling process, the temperature of the wafer 56 is againmonitored by the infrared sensor 62. Once the wafer 56 is cooled to atemperature close to a room temperature (within about 5° C.), the wafer56 is moved from the cooling station back to the cassette or to thesurface measuring station.

[0035] A benefit of the photo-thermal surface treatment apparatus isthat the surface treatment apparatus may be integrated with an in-line,real-time testing apparatus, such that electric characteristics of thesurface treated wafers can be measured. For example, AC photovoltageinduced at the surface of the wafers can be measured and analyzed.

[0036] Electrical characteristics of p-type wafers, photo-thermalsurface treated at various temperatures, have been measured. ACphotovoltage induced at the surface of the wafers have been measured andanalyzed with a method described in U.S. Pat. No. 4,544,887 and U.S.Pat. No. 5,661,408. Carrier lifetime, doping concentrations,conductivity type and depletion width have been determined from thesurface photovoltage measurements. Referring to FIG. 6, electricalcharacteristics of p-type epitaxial layers depend on the maximum or peaktemperature reached by the wafer during the illumination cycle. In theembodiment of FIG. 6, the time required to reach the peak temperatureduring treatment was about 30 seconds. Immediately after reaching thepeak temperature, the illumination was turned off and the wafer waspermitted to cool. Wafers were measured at room temperature after eachheating-cooling cycle.

[0037] The surface charge, Q_(s) [q/cm²], and the reciprocal of thesurface recombination lifetime, 1/τ[1/μsec], were measured for two p/p+silicon epitaxial wafers with epitaxial layer resistivities of 1.4ohm-cm and 30 ohm-cm, respectively. The surface charge of the wafersincreased after each heating-cooling cycle, reversing the change insurface charge due to exposure to the clean-room air for about 2 hours.With further increase in temperature, the surface charge reached itssaturation value corresponding to the surface inversion. Similarly, thereciprocal of the surface recombination lifetime changed with theprocessing conditions, reaching saturation at about the same temperatureas the surface charge. The same dependence on processing conditions wasobserved independent of the resistivity of the wafer and wafer cleaning.This is demonstrated in FIG. 4, which shows two epitaxial wafers, oneas-grown and one SC1+SC2 treated, both reaching about the same targetvalue after photo-thermal treatment. For temperatures exceeding thetemperature at which the surface charge and the reciprocal of thesurface recombination lifetime reached the saturation value, furtherillumination beyond the time required to reach a peak temperature didnot affect the measurements. At lower temperatures, the measured valuesincreased slightly with increased illumination time.

[0038] In general, processing conditions required to reach saturationdepends on wafer parameters. They depend, for instance, on the waferdiameter and thickness. They may be different for CZ and epitaxialwafers. A wafer coating (e.g., thermal oxide coating) is also expectedto change treatment conditions.

[0039] Photo-thermal treatment restores positive surface charge andinversion conditions, which allows the establishment of referenceconditions for determining specific parameters of the wafers. Twoimportant parameters include near surface doping concentration, N_(SC)and surface recombination lifetime, τ. These parameters can bedetermined from the measurement of the AC surface photovoltage performedunder conditions as described in U.S. Pat. No. 4,544,887 and U.S. Pat.No. 5,661,408.

[0040] Referring to FIG. 7, the apparent doping concentrations ofas-grown p-type silicon epitaxial wafers before and after photo-thermaltreatment at peak temperature of 250° C. are compared. The abbreviationPTT refers to photo-thermal treatment. The doping concentrations weremeasured with an assumption that each wafer surface was at inversion.For all measured wafers, the apparent doping concentrations deviatedfrom a target value more before photo-thermal treatment then after thetreatment. The values after surface treatment were within expected waferbatch uniformity.

[0041] Referring to FIG. 8, doping concentrations of RCA cleaned p-typesilicon epitaxial wafers are compared before and after photo-thermaltreatment at peak temperature of 250° C. The measurement conditions werethe same as for the wafers of FIG. 7. The measured doping concentrationsdeviated from a target value more before photo-thermal treatment thenafter. The deviation before photo-thermal treatment was about an orderof magnitude higher than for the RCA cleaned epitaxial wafers than forthe as grown wafers shown in FIG. 7.

[0042] Having shown the preferred embodiment, those skilled in the artwill realize many variations are possible, which will still be withinthe scope and spirit of the claimed invention. Therefore, it is theintention of the applicant to limit the invention only as indicated bythe scope of the following claims.

We claim:
 1. A method for in line, real-time processing and monitoringof a semiconductor wafer comprising: creating a plurality ofelectron-hole pairs near a surface of the wafer; and heating the waferto substantially desorb any contaminant adsorbed on the surface of thewafer.
 2. The method of claim 1 wherein creating a plurality ofelectron-hole pairs comprises illuminating the wafer with radiationsufficient to create a plurality of electron-hole pairs near the surfaceof the wafer.
 3. The method of claim 2 wherein heating the wafercomprises illuminating the wafer with a near infrared radiation.
 4. Themethod of claim 2 wherein heating the wafer comprises placing the waferon a hot surface.
 5. The method of claim 2 further comprisingautomatically controlling intensity and duration of heating andilluminating steps.
 6. The method of claim 2 further comprisingmeasuring a temperature of the wafer during the heating step andcontrolling intensity and duration of heating and illuminating stepsbased on the measured temperature.
 7. The method of claim 2 wherein thewafer is heated and illuminated until a stable surface condition isachieved.
 8. The method of claim 1 wherein heating comprises heating thesubstrate to a temperature in the range from about 200° C. to about 300°C.
 9. The method of claim 3 wherein illuminating with a near infraredradiation comprises illuminating with light having a wavelength in therange from about 0.2 microns to about 0.4 microns.
 10. The method ofclaim 2 further comprising cooling the wafer after heating andilluminating the wafer.
 11. The method of claim 2 wherein the wafer is ap-type wafer and heating and illuminating the wafer restores aninversion layer at the surface of the p-type wafer.
 12. The method ofclaim 2 wherein the wafer is a p-type wafer and heating and illuminatingthe wafer activates dopants previously deactivated due to interactionswith contaminant ions.
 13. The method of claim 1 further comprising:illuminating a portion of the wafer with a modulated light; andmeasuring an electrical characteristic of the wafer.
 14. The method ofclaim 13 wherein measuring an electrical characteristic comprisesmeasuring a photovoltage induced at the surface of the wafer.
 15. Themethod of claim 14 further comprising calculating a carrier lifetimefrom the measured surface photovoltage.
 16. The method of claim 14further comprising determining a conductivity type from the measuredsurface photovoltage.
 17. The method of claim 14 further comprisingdetermining a doping concentration from the measured surfacephotovoltage.
 18. An apparatus for surface treating a semiconductorwafer comprising: a surface treatment chamber; and a source of radiationilluminating a semiconductor wafer disposed inside the chamber with aradiation sufficient to create a plurality of electron-hole pairs near asurface of the wafer and to desorb any contaminant adsorbed on thesurface of the wafer.
 19. The apparatus of claim 18 wherein the surfacetreatment chamber is integrated with an inline, real-time testingapparatus, such that electrical characteristics of the wafer can bemeasured.
 20. The apparatus of claim 19 wherein a surface photovoltageof the wafer is measured after the wafer has been surface treated. 21.The apparatus of claim 18 wherein the source of radiation comprises atungsten halogen quartz lamp.
 22. The apparatus of claim 18 furthercomprising a plurality of reflectors disposed inside the surfacetreatment chamber to provide uniform illumination of the wafer.
 23. Theapparatus of claim 18 further comprising a power control circuitry forcontrolling an intensity of radiation from the radiation source.
 24. Theapparatus of claim 18 further comprising a temperature sensor formonitoring radiation from the wafer during surface treatment.
 25. Theapparatus of claim 18 further comprising a filter disposed between theradiation source and the wafer for filtering radiation having wavelengthgreater than about 4 microns.
 26. The apparatus of claim 18 furthercomprising a first filter disposed between the radiation source and thewafer, a second filter disposed adjacent the first filter, and an airpassageway disposed between the first filter and the second filter forcooling the filters, wherein the first filter and the second filterprevents radiation having wavelengths greater than about 4 microns fromreaching the wafer.